The fourth man to come forward to accuse “Sesame Street’’ puppeteer Kevin Clash of inappropriate sexual contact says the voice of Elmo had trouble getting it up as he was trying to get down with his alleged victim.

“Kevin Clash told [his accuser] he had difficulty . . . due to a medical condition,” according to the new accuser’s civil lawsuit filed yesterday in Manhattan federal court.

The alleged victim, now 33, said he was about 16 when he first met Clash, then 35, in 1995 while walking on a Miami beach. The two started talking — Clash complimented him on his looks, the man said — and the pair kept in touch over the phone.

After learning that the accuser had problems at home and wanted to run away, Clash, the voice of Elmo for 28 years until he resigned last month, promised to “be a dad” to him.

Clash lured the young man to the city “with promises to pay for his plane ticket . . . and give him cash and a free place to stay,” according to the lawsuit, in which Clash’s latest accuser remains unnamed.

“[The accuser] had been abused by a teacher when he was 15 and was initially very leery of Kevin. But Kevin convinced him he would be safe” — by disclosing he was the man behind the world’s most beloved muppet, said the plaintiff’s lawyer, Miami-based Jeff Herman, who is also representing two other accusers.

“As soon as he got to New York, Kevin told him he was the voice of Elmo,” Herman said.

The accuser stayed with Clash only a few days, when the abuse is alleged to have happened.

Herman said that because Clash is alleged to have transported his accuser across state lines for the purpose of engaging in sexual activity, he could face criminal charges.

“The lawsuit is without merit, and we will vigorously defend the case and Mr. Clash’s reputation,” said Michael Berger, a lawyer for Clash, reiterating what the puppeteer’s camp has said each time the other claims were made public.

A doorman at Clash’s Upper West Side apartment building yesterday said the Muppet master, a divorced dad with a college-age daughter, has not been seen in some time.

The latest accuser said that being a parental figure was a role Clash liked to play — and another alleged victim has echoed that.

“ ‘Mr. Tickler’ is what I will call him, and the game we played was father and son,” a previous accuser, who claims he also was 16 when he and Clash hooked up, wrote in an unpublished memoir.

Herman added yesterday: “These are all vulnerable boys. None of them had father figures in their lives, and they were looking for that father figure. There’s a consistency.”

Abuse charges against Clash, now 52, first surfaced last month.

After the first accusation was made public, Clash released a statement that said he was gay and admitted the relationship but said it was between two consenting adults. He resigned when a second accuser came forward — college student Cecil Singleton, now 24, who sued him for $5 million.

Singleton and another accuser said Clash was trolling for young boys on a gay telephone chat line and that he lied about his age.

Herman said other possible victims have been in contact with him and that he is in the process of vetting them.